Avalanche Forecast

Issued: Feb 5th, 2018 4:53PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada jmcbride, Avalanche Canada

There is some uncertainty as to how much snow is expected for Tuesday. Danger ratings will increase if amounts received exceed 5-15 cm as forecasted.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

TUESDAY: Cloudy, flurries. Accumulation 5-15 cm. Ridge wind moderate, southwest. Temperature -2. Freezing level 600 m.WEDNESDAY: Snow. Accumulation 15-25 cm. Ridge wind light gusting to strong, west. Temperature +2. Freezing level 1700 m.THURSDAY: Mix of sun and cloud. Ridge wind light, northeast. Temperature -1. Freezing level 800 m.

Avalanche Summary

Sunday north of Meziadin Junction a natural size 4 and a natural size 3.5 were observed on a southwest and northeast aspect at 1800-2000 m and are suspected to have failed on the mid-January layer.On Saturday wind and storm slab avalanches failed naturally to size 2 on a variety of aspects in both alpine and treeline elevation bands. A natural size 3 persistent slab avalanche was observed on a steep north facing alpine feature with a crown up to 100 cm in depth, which suggests the mid-January interface was involved. A another very large avalanche (size 3.5) was reported from an unknown aspect/elevation. Natural avalanche activity was observed on Friday morning, producing several 30 cm thick slabs in the latest snow. A large (size 3) storm slab avalanche was reported on a east aspect east of Terrace.A few persistent slab avalanches released on Wednesday, most likely failing on the mid-January crust. This included a natural size 3 avalanche on a southwest slope at 1150 m near Exstew and a few skier triggered slabs (size 1-2) in thinner snowpack areas (east of Terrace and the northern part of the region).

Snowpack Summary

Another 15-25 cm of new snow since Sunday morning brings settled storm snow accumulations to 50-80 cm over the past week. A weak layer buried in mid-January is 100-140 cm below the surface and remains a concern. In most areas this layer is a crust, but it may also be surface hoar in sheltered areas at treeline and below. This layer produced a few human triggered avalanches throughout the region over the past week, and may remain reactive as it adjusts to the weight of the new snow.In thinner snowpack areas (north and inland), deeper crust / surface hoar layers that were buried in December and early January may still be a concern. They are buried over 150 cm below the surface, but may be triggerable from shallow spots.

Problems

Storm Slabs

An icon showing Storm Slabs
Significant snow and wind have formed storm slabs that have been reactive to both human and natural triggers at higher elevations and in wind-affected terrain. More snow and wind will continue to build these slabs.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Be careful with wind loaded areas, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs
A weak layer exists 100-140 cm below the surface. It may still be possible for humans to trigger persistent slab avalanches on this layer, or for a storm slab release to step down to this layer resulting in a very large avalanche.
Caution around convexities or areas with a thin or variable snowpack.Avoid areas with overhead hazard, avalanches triggered higher up may travel long distances.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2.5 - 4

Valid until: Feb 6th, 2018 2:00PM